Ground anchors are commonly used to support various structures and for use by utilities for anchoring supports, utility poles, and the like. The anchors often have an elongated shaft with a square or round cross-section. A top end of the shaft has a drive connection for coupling to a rotating drive assembly. The bottom, ground engaging end has one or more helical outwardly extending load bearing plates fixed to a hub.
U.S. Pat. No. 4,981,000 to Hamilton et al. discloses an earth anchor having a helical plate and a flattened lead tip. The center of the lead tip as shown appears to be aligned with the center axis. The angle of the cutting edge is positioned such that the apex leads the point at the intersection between the second cutting edge and the helical blade to facilitate movement of the soil around the hub. FIG. 7 shows the face of the leading tip angled outwardly from the center axis and aligned with the leading edge of the helix.
One example of a screw anchor is disclosed in U.S. Pat. No. 4,334,392 to Dziedzic. This device is a modular screw anchor having an elongated rod with one or more specialized anchor members. The shaft also includes an obliquely oriented beveled earth penetrating lead to facilitate installation in rock soils. The anchor has a tubular, rod-receiving hub having a polygonal cross-section. An outwardly extending helical blade is fixed to the hub.
U.S. Pat. No. 5,408,788 to Hamilton et al. discloses a screw anchor having a hollow hub for receiving a wrench. A helical, load bearing element projects outwardly from the hub. An elongated, pointed spade extends from the end away from the hub. The spade has two diametrically opposed angular cutting margins on opposite sides of the hub.
U.S. Pat. No. 4,617,692 to Bond et al. discloses a drilling tip and expansion anchor for drilling a hole in a wall. The threaded shaft is rotated in a first direction to expand the anchor with a drill tip attached to the end of the shaft. The shaft is then rotated in the opposite direction to unscrew the shaft from the tip.
U.S. Pat. No. 4,750,571 to Geeting discloses a drilling apparatus having a disposable tip. A disposable cutting tip is attached to the auger section which is positioned within the ground screen. The tip is attached to the auger by a shear pin or bolt. The shear pin breaks when the auger is removed from the ground thereby leaving the drill tip in the ground.
U.S. Pat. No. 4,898,252 to Barr discloses a cutting tip for a rotary drill bit. The drill bit includes a wear surface attached to a plurality of plates forming the carrier for the cutting element. As the cutting edge wears, the plates break away to increase the clearance of the rear portion of the cutting edge and reducing the size of the wear surface to reduce the resistance to drilling.
U.S. Pat. No. 5,899,123 to Lukes discloses a threaded fastener having a drill point connected to the threaded fastener by a frangible line. The drill tip drills a hole through the work piece until the drill tip engages an inclined surface thereby causing the drill tip to break away from the threaded fastener.
U.S. Pat. No. 6,588,515 to Wentworth et al. discloses a rock drilling bit with a plurality of cutting teeth raked into the cut of the drilling bit. The teeth are angled at about 30° to provide the shear cutting force. The arrangement of the teeth reduces shock and vibration applied to the housing.
U.S. Pat. No. 7,182,556 to Takiguchi et al. discloses a drill with a disposable insert tip. The drill has a drill main body and an insert that is attached to the main body. The end of the main body has a plurality of guiding grooves shown in FIG. 2. The removable tip has convex portions that engage the guiding grooves. The drill does not have a frangible or break away portion.
U.S. Pat. No. 8,109,700 to Jordan et al. discloses a replaceable tip for a bit or auger. As shown in FIG. 1, the replaceable tip has a threaded shaft that is threaded into the threaded bore in the shaft of the auger. In the embodiment shown in FIG. 5, the auger has an end portion that is removably coupled to the shaft of the auger. The tip of the auger does not include a frangible portion.
While these prior devices have generally been suitable for their intended purpose, there is a continuing need in the industry for improved ground anchors.